The present invention relates to an organic solvent-based dispersion of conductive tin oxide powders having excellent dispersibility and excellent transparency, and an organic solvent-based conductive paint using the same.
The conductive paint of the present invention is useful for static prevention of the display surface of a display device, its surface protecting material, a transparent substrate such as a film, etc., and is also useful as infrared shielding for building materials, window materials of vehicles, etc.
A variety of transparent substrates including display surfaces for display devices such as cathode ray tubes (CRT), liquid crystal displays (LCD), etc., window mate rials for clean rooms, glass or plastics used as packaging materials for IC packages, or films used for OHP or photographs, etc. are generally insulating and thus tend to be electrically charged. For this reason, dusts or trashes are apt to attach to the surfaces of these materials. In electronic devices, static electricity causes problems of incorrect working, or the like.
Attempts to solve these problems have been made typically by kneading conductive powders into transparent substrate materials and then molding the kneaded powders, or by coating conductive powder-incorporated paints onto the surface of such substrates. Tin oxide powders are suitable as conductive powders for these applications, since they can retain excellent transparency, if uniformly dispersed in a medium, and have excellent conductive properties. For use in organic solvent-based paint, however, tin oxide powders are only sparingly dispersible in paint due to its extremely strong hydro-philicity, resulting in failure to obtain sufficient transparency.
In order to improve the dispersibility of tin oxide powders in organic solvent-based paint, there is known a method in which a dispersant such as a surfactant or the like is incorporated into paint. According to the method, it is required to incorporate large quantities of a dispersant into paint for achieving sufficient transparency, which, when coated, leads to poor adhesion to a substrate material and reduction in coating strength. Furthermore, these conductive tin oxide particles are after all coated with such a nonconductive dispersant at the surface thereof to decrease the conductivity.
The present invention has overcome the foregoing problems by providing an organic solvent-based dispersion of conductive tin oxide powders, which have excellent dispersibility even when the amount of the dispersant is minimized as possible, and when used in organic solvent-based paint, exhibit excellent transparency, conductivity and adhesion, and by providing conductive organic solvent-based paint obtainable by formulating the dispersion above.
As a result of extensive studies, the present inventors have discovered that, when conductive tin oxide powders coated with an organic metal coupling agent are dispersed in an organic solvent-based medium in the presence of a dispersant, the resulting dispersion provides a good dispersibility even in a greatly reduced amount of the dispersant to be added, and a mixture of the dispersion and resin provides excellent transparency and conductivity with excellent physical properties for coating. The present invention has thus been attained.
That is, the present invention relates to a organic solvent-based dispersion of conductive powders comprising an organic solvent-based medium as a dispersion medium, tin oxide powders coated with an organic metal coupling agent at the surface of the tin oxide particles and a dispersant. The present invention further relates to conductive paint comprising a mixture of the dispersion and resin.